LAUSR

Abstract Pink, blue, and red hydrangea [(Hydrangea macrophylla subsp. Macrophylla var. macrophylla (Thunb.)] cultivars contain the anthocyanin pigment delphinidin-3-glucoside that color the sepal. Without aluminum (Al), the natural color of the pigment is pink or red depending on the cultivar. To produce blue sepals, plants are fertilized with Al2(SO4)3 (AS) under low phosphorus (P) conditions. To determine the effect of AS on nutrient tissue concentrations ‘Early Blue’, ‘Hor Tivoli’, ‘Jip’, and ‘Mathilda Gutges’ plants were treated with 0 (pink), 12, or 15 g (blue) of AS. Pre-bloom leaf tissue concentrations were analyzed with blue cultivars generally having higher concentrations of sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), boron (B), copper (Cu), and Al, while the pink plants had higher nitrogen (N), P, calcium (Ca), and magnesium (Mg) concentrations. Concentrations of N, potassium (K), Mg, B and Cu were consistent with published sufficiency ranges regardless of color or cultivar, while S, Fe, Mn and Zn concentrations were below sufficiency in some pink cultivars. The P concentrations in both pink and blue cultivars and Ca in some blue cultivars were lower than the published sufficiency range. The difference in leaf tissue nutrient concentrations among cultivars and coloration, suggest that nutrient uptake in hydrangeas varies and that lab recommendations should be customized depending on cultivar and color production system.